Increasing use of pre-processed foods, both in homes and in restaurants and other group eating establishments, has created a continuously growing demand for high-capacity automated food processing equipment. That demand is particularly evident with respect to hamburgers, molded steaks, fish cakes, and other molded food patties. A single drive-in restaurant may serve hundreds or even thousands of hamburgers and other molded food patties each day; a group of such restaurants in a metropolitan area, using a single source of supply, may require many thousand patties daily.
Available automated food patty molding equipment is not well adapted to current high-volume demands. With available equipment, a single food processor may require a large number of molding machines to fulfill his sales requirements. A changeover from the patty size of one customer to that of another, especially if coupled with some difference in the specification for the meat or other moldable food, leads to an inordinate time loss, dissipated in machine set-up time.
Pumping mechanisms for automated food patty molding machines are a source of several operational and maintenance difficulties. The moldable food tends to clog or to "bridge" in the feed apparatus, producing non-uniform patties. Food may collect in the feed mechanism, producing possible spoilage problems. Commonly used non-yielding compressors such as paddle pumps, synchronized with the molding mechanism, often produce a non-uniform feed pressure. The filling pressure fluctuates with machine timing, product viscosity, and the quantity of product that falls in front of the paddles in each cycle; as a result, the mold cavities may be over-filled or under-filled on any given stroke.
Yielding compressors, as used in some conventional machines, utilize springs to back up the food compression pumps; the spring force pushes the food into the mold cavities. On each cycle of the molding mechanism, the compressor opens to receive more food material. The amount of food material captured varies the degree of spring compression, and thus varies the filling pressure, so that underfilling or over-filling may occur. A product exhibiting poor flow characteristics is also difficult to feed into the compression system. Consequently, when full pressure is most needed, it is likely to be unavailable, producing an inconsistent product.
Variation in the pumping pressure to compensate for food material differences may be necessary to obtain a uniform product. Non-yielding paddle pumps often produce inadequate pressures on low-viscosity food materials and excessively high pressures when the material viscosity is high, as when the material is too cold or too dry. Spring adjustment can compensate for some of these differences, in known yielding compression systems, but the range of adjustment is limited, and effective adjustment is often quite difficult for the operator to achieve. The synchronized pumps of both types produce excessive noise levels, often extremely uncomfortable for operating personnel.